Figs. 3, 12. Chana Member of Pecatonica Formation. Dolomite, nonargillaceous, sandy, thick-bedded. Thickness about 6 feet. Shown on columnar section as underlying Dane member (new) and overlying Hennepin member (new). Age is Middle Ordovician.
[Notable exposures in Dixon-Oregon area, northern IL.]

Source: US geologic names lexicon (USGS Bull. 1200, p. 715).

Member is 6.2 ft thick at type section. In northern outcrop area, is commonly less than 5 ft thick, but reaches 20 ft in southern IL. In northern area, consists largely of brown, thick-bedded, vuggy, pure dolomite containing disseminated sand grains and, in places, thin beds of sandstone of the St. Peter texture. Basal part commonly has slightly argillaceous or shaly beds and phosphatic pebbles. In southern IL, unit is largely pure, thick-bedded limestone.

Source: GNU records (USGS DDS-6; Reston GNULEX).